The present invention relates to antennas and more particularly to an antenna system with a multi-port array of partially shared radiating elements.
Antenna systems with arrays of patch radiating elements are useful for various wireless communications applications, and particularly in fixed wireless access. Where such antenna systems are produced in large quantities, it is important that the antenna systems be reliable and inexpensive, and have minimum radiating area or aperture size.
Prior known antenna systems have used multi-port, fully shared arrays. U.S. Pat. No. 4,464,663 to Lalezari et al. and U.S. Pat. No. 6,359,588 to Kuntzsch each disclose an antenna having two elements with each element having dual polarization. U.S. Pat. No. 6,121,929 to Olson et al. discloses an antenna with a two by two array of dual slant 45 linearly polarized elements. Such fully shared arrays with dual polarized elements can provide dual use of a frequency or use of two frequencies while requiring about half the aperture area and half the number of elements as would be required with arrays of unshared elements.
A single layer or monolithic feed layout for an array of patch radiating elements avoids expensive and unreliable cross-overs and feed throughs. As the number of radiating elements in a multi-port array with a single layer feed layout increases, the feed network topology becomes more complex and the feed lines become significantly longer. The prior known fully shared arrays that have simple feed network topology with relatively short feed lines were therefore limited to a two by two array size.
An antenna system includes a ground plane, an aperture array of patch elements and a feed structure. The feed structure has a first beam forming network and a second beam forming network. The first beam forming network is coupled to a selected first group of elements at a first angle to form a first antenna array having a first polarization. The second beam forming network is coupled to a selected second group of elements at a second polarization angle to form a second antenna array having a second polarization. The patch radiating elements of the aperture array are partially shared by the first and second antenna arrays, with the first and second antenna arrays sharing at least one but less than all of the elements. By partially sharing elements of multiple arrays one can more efficiently layout the array beam forming networks of each array and minimize the size of the combined aperture.